#include<fstream>
#include<queue>
#include<algorithm>
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");
struct oaie {
    int dist;
    int puf;
} a[100002];
/*bool cmp(oaie a, oaie b)
{
    if(a.dist==b.dist)
        return a.puf>=b.puf;
    return a.dist>=b.dist;
}*/
priority_queue <int, vector<int> > heap;
int n, d, l, k, s, i, t[100002], tmax;
int main ()
{
    f>>n>>d>>l;
    for(i=1;i<=n;i++)
    {
        f>>a[i].dist>>a[i].puf;
        t[i]=(d-a[i].dist)/l+1;
        if(t[i]>tmax)
            tmax=t[i];
        if(t[i]<0)
            t[i]=2147483648;
    }
    //sort(a+1,a+n+1, cmp);
    for(i=tmax;i>0;i--)
    {
        for(int ii=1;ii<=n;ii++)
            if(t[ii]==i)
                heap.push(a[ii].puf);
        s+=heap.top();
        heap.pop();
    }
    g<<s;
    return 0;
}